Preparation of cellulated glass bodies



Patented July 4, E56

or cELLULA BODIES PREPARATION in: Grits.

Walter D. Ford, Port Allegany, rt assignor to Pittsburgh Corning Corporation, Allegheny County, Pa., a corporation of Pennsylvania N o Drawing. Application January 12, 1949,

Serial No. 70,602 i I-The present invention relates to the preparation ,of .cellular b'odies suitable for use asthermal insulation, as buoyant elements in life rafts,

I floats for fish nets and for other purposes of similar nature. In particular, the inventionfrelates to the 'p'reparationof cellular bodies by sintering a mixture of finely pulverized glass and an agent "thermally reactive, "to produce bloating gases in the sintered mass.

' One object of the invention is to provide a process of preparing cellular glass from pulverulent glass anda gassing agent by sintering powdered glass in the presence of agassing agent in which cellular bodies of light weight, uniform structure and completely sealed cells can be obtained economically. and without adhesion to the Walls of the molds in which the cellular bodies are formed. a

These and other objects of the invention will be apparent from consideration of the following specification and accompanying claims.

It has heretofore been proposed to form cellular glass bodies by heating, to sintering temperature, a mixture of finely pulverized glass and a small amount of a pulverulent gassing agent; such I as carbon black, calcium carbonate, or the like.

In order to assure smooth and uniform cellulation of this product, when the mixture is heated, it is also customary to incorporate with the mixture a small amount of antimony-trioxide. When such mixture is placed in a suitable refractory mold in appropriate amount and heated to a" temperature slightly above the .sintering point of the glass content, the particlesof glass become welded together Without complete fusion. Closed pores are thus formed and, simultaneously, chemical reaction of the gassing'ag'ent occurs to form gases in gradually increasing volume which expand the pores in which they are entrapped,-- to form a bloated body of low density and consisting of a myriad of tiny cells or bubbles of glass, in a coherent froth-like mass. Such bodies, by reason of their cellular structure, are

of high insulating value against the transmission of heat, and are also impervious to gases, vapors and liquids. The bodies, therefore, are suitable for use in place of cork or asbestos as a heat insulating medium and, because of their resistance powdered carbon that will becombustible.

to permeation by moisture, chemical ag'encies-,-

resistance tofire, vermin, and other agencies of deterioration, are in many respects superior to the materials which they replace. The low density also admits of the use of the material as a 4 Claims. (Cl. 105-40) 'suitable partingagent designed toovercome the adhesion 'but still, difficulty has persisted.

The present invention isbased, in part, upon the discovery that. this. adhesion between the cellulatirig'mas's and themolds is due, at least in 'part;1to the presence of the antimonytrioxide employedto promote .cellulation. T It seems to be, in part,,]evaporated before cellulation and, in

some way; facts at the glajss-mold interface to'produce adhesion. It hasjlnowbeen found that the difiiculty can be substantially orcompletely obviated, byireplac'ement ofthe antimony trioxide by a carefully regulated amount of alkaline earth sulfate, notably the sulfate of calcium which is actually ground up or thoroughly admixed with the powdered glass and carbon. The resultant product compares well, in uniformity and degree of cellulation, with the conventionally prepared material.

In the operation of the invention, a glass of conventional formulation may be employed. For example, it may comprise ordinary lime soda glass such as is employed in windows, and which consists essentially of silica, lime and soda ash in appropriate amounts, as is well understood. This "glass may also be modified by the inclusion of certainamounts'of other ingredients, such as alumina, magnesium, borax, etc. A" part of the soda ash, constituting the source of alkali metal in the glass, may also be replaced with sodium sulfate, which probably is largely decomposed to form sodium oxide during the fusion of the raw batch to form the glass.

The glass is finely pulverized, for example, to particle size, such that it will pass a screen of 200 mesh, or even 300 or 400 mesh per square inch. This finely pulverized material may be ground with the gassing agent, e. g., finely divided carbon; such as lamp black, carbon blacks, e. g., channel black, powdered coal, powdered charcoal, powdered graphite, or any other form of finely The amount of finely divided carbonaceous material v is susceptible of certain variation but, in any event, the amount'required is never very large. (A range of .l to 1 percent is good.) For example, in lamp black, the ratio will be approximately 0.5 to 1 percent, although slightly larger or smaller amounts may be employed. With carbon black, the ratio is even smaller, e. g., .15 to .2 percent.

packing or buoyant element .in life rafts, buoys,

floats for fish nets and many other poses. 7

The process, as thusoutlined, has heretofore been brought, in many respects, to a high degree similar purthe mixture to adhere, during thebloatingoper- I6 tion, to the surfaces of the molds in which the' percent of CaSO4 H2O. However, this amount may be increased slightly; for example, to 0.2 of perfection." However, difficulty has heretopercent or possibly even slightly more. The calcium sulfate may be in substantially any desired exposure to air before or after incorporation" with the glass, the dihydrate "ofthe formula CaSO4.2HzO is to be preferred. The ratio of the calcium sulfate above given is based upon thouse of the half hydrate (CaSOd/ H 2'O). Necessary adjustment for the difference in molecular-' weight At the conclusion of the heating and cellulatlng operation, the product is'partially cooled, the molds removed and the blocks or slabs then subjected to a slow and careful annealing operation with gradually reducing temperatures over a period of several hours. The resultant product, where it contacts with the mold surfaces, is smooth and free from holes, such as are likely to characterize products prepared from mixtures of the anhydrous material or theqll lidfflfi an .Q cqntainingantimony trioxide as an aid to the ead ly be c lculated. U ua qu a a p c'ellulation. The product, preferably in the form results can be attained by the use of 0.1; perce qfslabs can be cut to size and shape and is suit- O e (I y h ch is the eqlllvalefit f able 'for' the same uses as the conventional prodpercent of the half hydrate. A not in which antin oiiy trioxide is employed. "The*components of the mixture above de- 1 The cells are closed and thehe'at insulation value -'scribed are very carefully'admixedyfor example, sllb l flnfi ny c 'em i as that o hev envnby gradual or; periodicaddition of thecarbon tiorial product. and calcium sulfate tothe'glass cullet'as 'it'is The invention particularly contemplates; the e ground uponiheiballmfllv u e f ca i m a a he remou e'ifaeen The pulverized material is placed in a su table but-the use offother alkaline'earth'metal sulfates, mold, such; as a sheet steel mold,'"f ormed"of a such as barium sulfateor theflike, is also highly refractory nickel-chromium alloy steel and ontemplated; comprising upper andlower' sections similar in Indeed, t, if t all, of th ulfates of s r t re n n na br p o e o alkaline earth metals canfbe so employed, The which'may be invertedover the other to form a following constitute some of the sulfates "which closedcontainerz' "This mold is; preliminarily coathave been t t d found ff ti i "*1 its t wltlhl fi a pattmg Sodium sulfate (NaeSO4, Salt Cake) agent such as a mixture of clay and aluminum V r r l c Lithium sulfate (Ll2SO'4.H20, C. P.) hydrate, in the formof awater slurry towhichan Cal .umvsulfat (C so 1/H2O. 1 t organic binder sucha's dextrine has been addedulf P p a i aft/11s P e e the m n 5 adjusted Zirf fir ateizns 'TI- fdC P) approximately,'to one-seventh the volum e of the Al 0 2 H v .4 a r uminum sulfate (Al2(SO4)3.18I-I2O, C. P.) mold. When so ad usted the resultant cellu Titaniumpsulf te (THSOJMQHO c lated'produc 11151111111118 moldhem d Ch omium t (c (8 0 rao r are heatedin a convenient manner, for example, r S a 9 r2 4 w l r Manganous sulfate (MnSO4.H2O, C. P.) in a roller hearth type furnace which operates n H t c I r 1 e Feiric sulfate (re2(SO4)3.H2O, C. P.) continuously. The powdered mixture is, itself, V o l .w H 1 y V a Cobaltous sulfate (CoSOMI-IzO, C. P.) h ghly resistant to transmission of heat and, Nibkelsulf (Nisotsmo C P) therefore, the heat progresses relatively slowly at e r o 1 e- 'through'the mass, usually requiring several hours 40 The fqllow ne a are. ken re ia. Series of wreath compl he te a h ul is" cofiductd to d t rmin the. Synergistic reach approximately 1690, 1659 or 1750? E, deefiect ofe ach of the foregoing sulfates i t pending wh upoet he at e th las a m xtu o finel pulverize 'a ae m ln ne employed as'a source of material. of" lamp black Sulfate Percent i -ggg -i Cell Size Cell Structure Percent v v. Standard Normal Good. NazSO; 0.1 Slightly larger Do, V thannoi'iiial. Do [L2 'do Do. Ll2SO4.HzO 0.1] D0. D0 p 0.2 Do. CaSO4.%HzO 0.2 D0. D0. 0.4 Do. BfiSOL- 0.2 l 13 8: I 0 L A]2(S04)3.18H20 0.1 fii Do 0:2 Do. 8 8'? 5 si' 1 3;?

0 r' rusmmmo. 0.2" at odz' Do 0:4 -Do. D0 0.8 Slightly irregular znsorvmo.-- 0.2 03%? W 0.4 Do. Do 0.23 Db. OIQ(SO4)3.5H2O, 0:51 DO. Do ,0.-2 Do.-

83 Sl' t1?- M11804 H2 011 gia r D 0.2 1 Do. Do 0.4" Do. reusolm-nzo o. 2 Do. Do 0.4 Do. 00804.7Hz0 or a Do. Do 0.2 Do. Do- 0.4 .do Do. D 0.8-j Slightly lei-germ Do. NiSOifi 0.1 100: Normal- Do.- -13 0. Do. Do- 0.4 s Do.- Do 0. 8 f (1 Do.-

The forms of the invention herein disclosed are to be considered merely as exemplary. It will be apparent to those skilled in the art that numerous modifications may be made therein, without departing from the spirit of the invention or the scope of the appended claims.

This application is a continuation-in-part of my co-pending application, Serial No. 590,116, filed April 24, 1945, now abandoned, and entitled Preparation of Cellulated Glass Bodies.

I claim:

1. A process of forming cellular glass of uniform structure, having closed cells, which comprises admixing glass, pulverized to pass a screen of 200 mesh, with approximately 0.5 percent of finely divided carbon and about 0.1 to 0.2 percent of calcium sulfate calculated as hydrate, placing the mixture in molds and heating the mixture to the sintering point of the glass to form coherent cellular bodies, and cooling and annealing the bodies.

2. The process as defined in claim 1 in which the mixture is heated to a temperature about 200 F, above the initial softening point of the glass.

3. A process of forming cellular glass of uniform structure, which comprises admixing pulverulent glass with finely divided carbon in amounts of 0.1% to 1.0% by Weight of the mixture and 0.1% to 0.4% by weight of an alkaline earth metal sulfate, placing the mixture in a closed mold and subjecting it to heat about 200 F. above the sintering point, and subsequently annealing the product.

4. A process as defined in claim 3 in which the temperature of heating is approximately 1600 to 1650 F.

WALTER D. FORD.

REFERENCES CITED Country Date Great Britain 1936 N umber 

3. A PROCESS OF FORMING CELLULAR GLASS OF UNIFORM STRUCTURE, WHICH COMPRISES ADMIXING PULVERULENT GLASS WITH FINELY DIVIDED CARBON IN AMOUNTS OF 0.1% TO 1.0% BY WEIGHT OF THE MIXTURE AND 0.1% TO 0.4% BY WEIGHT OF AN ALKALINE EARTH METAL SULFATE, PLACING THE MIXTURE IN A CLOSED MOLD AND SUBJECTING IT TO HEAT ABOUT 200* F. ABOVE THE SINTERING POINT, AND SUBSEQUENTLY ANNEALING THE PRODUCT. 